The present invention relates to a system for controlling the position of a wheeled vehicle and, more particularly, to a position control system for maintaining a vehicle in a proper position when the vehicle is steered to make a turn, braked or abruptly started to run.
Implementations for supressing tossing or rolling of a vehicle body during a turn have been disclosed in, for example, Japanese Patent Laid Open Publication No. 56-42739/81 and Japanese Utility Model Laid Open Publication No. 56-147107/81. The disclosed type of system is constructed to temporalily increase the damping forces of hydraulic suspension units, or shock absorbing units, when the steering wheel of a vehicle is manipulated in the course of a travel at a speed higher than a given value, thereby offering occupants a comfortable ride and good operationability. This, however, suffers from a shortcoming which originates from the fact that the damping force is increased only for the duration of steering operation, that is, a condition causative of rolling, and thereafter immediately lowered to the original magnitude. For example, when the vehicle is steered to change the lane, the prior art system may prevent the vehicle body from tossing sideways but allows it to toss back in the other sidewise direction due to inertia immediately after the steering. In this respect, the prior art system is not always successful to effect the expected anti-rolling function. Further, while the vehicle runs offroad clearing a number of turns, the return of the damping force to the original small one occurs every time the vehicle is steered to the right or the left. This not only gives the occupants undesirable feeling but significantly lowers the durability of the system, because the control means associated with the suspension units has to be frequently turned on and off.
Another important consideration for insuring a comfortable ride and stability of operation is suppressing nose-diving of a vehicle body due to sudden braking or squatting due to sudden starting. However, systems heretofore proposed for such a purpose, like the anti-rolling system stated, are designed to increase the damping force of the suspension units only while the vehicle is being braked or started and, hence, incapable of eliminating tossing of the vehicle body due to inertia, which is apt to occur after nose-diving or squatting.